The present invention relates generally to the packaging of current sensor systems for use in components, such as relays utilized with motor control systems, and particularly to Hall effect current sensors packaged to provide optimum performance and dependability while minimizing the effects of extraneous influences, such as electrical noise.
A variety of sensors are used to measure the amount of current flowing through a conductor. One such example is a Hall effect current sensor that measures current flowing through a conductor and provides an output signal proportional to the level of current. Hall effect current sensors offer several advantages over traditional current transformers such as a more compact size, higher current levels for a given size, and a larger frequency bandwidth.
Some Hall effect current sensors include a ferrous-based core that surrounds a conductor and a Hall generator. In fact, there are several approaches to constructing and packaging Hall effect current sensor devices. In one approach, a donut or toroidal-shaped ferrite core is provided with a cut slot that is positioned over a Hall effect chip vertically mounted on and soldered to a circuit board. The ferrite core is manually positioned relative to the Hall effect chip and glued to the circuit board. In another approach, a donut-shaped ferrite core, soldered Hall effect chip, and circuit board are placed inside a housing. The components are secured inside the housing with an epoxy potting compound that completely fills the entire housing cavity. The components are then oven-baked for several hours to cure the epoxy.
According to another approach, an overlapping lamination stack is inserted into a bobbin which contains a Hall effect chip soldered to a circuit board. The circuit board, bobbin, Hall effect chip, and lamination subassembly are secured within a two-piece housing. Right angle pin connectors are soldered to the same circuit board as the Hall effect chip and are utilized as a means to mechanically and electrically connect the Hall effect current sensor module to a primary circuit board.
Each of the above-described systems suffers from one or more drawbacks. For example, positioning of a Hall effect chip relative to a gapped core is difficult when utilizing manual gluing and locating techniques. In other approaches, the use of right angle pin connectors tends to provide a mechanically insecure connection that is subject to breakage under the shock and vibration levels experienced in industrial controls environments. Also, such right angle pin connectors can be bent easily, creating difficulty in assembly. In other approaches, the manual labor of placing a core, potting a core, and gluing the core to a circuit board is an inefficient and expensive manufacturing process. Additionally, the required curing cycle reduces production through-put and adds significant cost to the sensor. These and other drawbacks reflect a need for a more reliable and cost effective system for packaging Hall effect sensor devices that are used in a variety of industrial environments, e.g. relays utilized in motor control systems.
It would be advantageous to utilize a Hall effect sensor package that permitted use of an open-loop system in which the voltage signal output from the Hall generator could be directly used to sense or measure current.
The present invention features a Hall effect current sensor system. The system comprises a Hall generator and a core having a central opening sized to receive a current conductor therethrough. The core also includes a gap designed to receive the Hall generator. The Hall generator and the core are mounted to a first printed circuit board. The circuit board also has an opening to receive the conductor therethrough. The first printed circuit board is electrically and physically connected to a second printed circuit board. The circuit boards are arranged such that the axis of the central opening is generally parallel with the second printed circuit board.
According to another aspect of the invention, a current sensor system is provided for use in a motor control environment to sense current and to provide a corresponding output. The system comprises a primary printed circuit board, a core and a sensor. The core is formed from a lamination stack having a plurality of laminations lying generally parallel to a common plane. The common plane is generally perpendicular to the primary printed circuit board. The core includes a conductor opening for receiving a conductor therethrough and a gap extending through the lamination stack. The sensor is disposed in the gap to detect a magnetic flux in the core and to output a corresponding signal. The core is grounded to the primary printed circuit board to reduce or eliminate the effects of electrical noise on the conductor.
According to another aspect of the invention, a Hall effect current sensor system is provided. The system includes a first circuit board to which a Hall generator is electrically connected. The system further includes a primary circuit board electrically coupled to the first circuit board. The primary circuit board has a pair of surfaces and a perimeter edge. The system also includes a core having a gap that is sized to receive the Hall generator therebetween. The core further includes a conductor opening through which a conductor extends. The axis of the conductor opening is generally parallel with the pair of surfaces.